1. Field of the Invention
The invention relates to telecommunications and specifically to an enhanced signal transfer point (STP) which alters the point codes in telecommunications signaling and supports User Parts in addition to providing standard STP functionality. The enhanced STP can form a portion of a telecommunications system.
2. Description of the Prior Art
Telecommunications signaling is the transfer of information within and among telecommunications networks for use by the networks. Signaling information is used to operate the telecommunications networks so these networks can transfer other non-signaling information for the network users. A few examples of signaling operations are call set-up, congestion control, and network management, although there are many signaling operations. One well known telecommunications signaling system is Signaling System #7 (SS7). At present, SS7 is the primary signaling system used by United States telecommunications providers.
As is known in the art, and as will be discussed below, STPs route SS7 signaling within the SS7 network and manage the various signaling links which comprise the SS7 network. Routing is accomplished by processing the routing label of the SS7 message by the Message Transfer Part (MTP) functionality of the signaling point. The MTP is comprised of three levels. Levels 1 and 2 facilitate the transfer of SS7 messages from one point to another over an individual signaling link. Level 3 facilitates the transfer of SS7 messages over the SS7 network beyond the requirements of individual link transmission. In other words, levels 1 and 2 are concerned with transport over individual links whereas level 3 is concerned with transport over the SS7 network in general.
An STP accomplishes its routing task at level 3 through the use of point codes which identify the various signaling points in the network. The STP level 3 will identify the destination point code in an SS7 message and select the proper signaling link for routing that message. For example, if switch A signals a switch B through an STP, the message will contain the destination point code for the signaling point in switch B (and the originating point code for switch A). The STP will accept this signal off of one signaling link, read the destination point code, and place the message on the appropriate link for switch B.
An STP can also control the signaling network through the use of management messages generated at level 3. In the above example, if there were signaling links between switch A and the STP, the STP might signal switch A with instructions to avoid particular links which were congested or had failed.
Telecommunications networks are commonly faced with the problem of re-routing user traffic among switches. Traffic may need to be re-routed from one switch to another switch, from one switch to multiple switches, from multiple switches to one switch, or from one group of switches to a different group of switches. When traffic accessing a network is directed to a particular switch, the traffic is described as being homed to the switch. Traffic being homed to particular switches may need to be re-homed to other switches.
Re-routing the user traffic encompasses changing the connections between the switches. Connections between switches may be added and deleted to create new network architectures. Due to the relationship between signaling and network architecture, any change in architecture needs to be reflected in the signaling system. A common method for doing this is to re-program the switches to signal each other in accord with the new architecture. This a complex and time consuming task. Switches contain numerous data files which must be re-programmed in accordance with the new routing scheme.
One prior art system facilitated the transition of trunks from an old switch to a new switch. The system converted the point codes in signaling messages directed to the old switch in response to a change in a trunk assignment from the old switch to the new switch. The converter was placed between the switch and the STP so that it only handled signaling on the signaling link connected to the old switch. It used a look-up table to yield the point codes. Since particular trunks would be connected to either the new switch or the old switch based on an assignment, a table could be constructed to identify the particular trunk used on a call and convert point codes based on this trunk/switch/point code assignment. The prior art suggests placing this conversion function in an STP, but it does not disclose more on this point.
Although this prior art system may be adequate for the limited scenario encompassing the transition of individual trunks from an old switch to a new switch, it does not address the problem of changing network architectures beyond this limited scenario. The prior art system is designed to serve two switches which share a single switch load and a common signaling destination. In other words, the system is limited to a situation in which signaling which has already been routed to the old switch is split between the old switch and the new switch during the transition of loads between the two switches.
As a result of this limitation, several problems are not addressed by the prior art system. Since it is based on identifying individual trunks for point code conversion, signals that cannot be associated with a specific trunk would not be able to have their point codes converted. The prior art system does not address the problem of handling management messages which are generated for the control of the signaling system. Also, the reliance on individual trunk identification does not adequately address situations in which entire switch loads are moved between switches, or when multiple switch loads are consolidated on a single switch. Because all trunks between switches are being changed over, individual trunk recognition is unnecessary.
Importantly, the prior art system does not identify the origination of the signaling message in order to select a destination for the signaling. The prior art system does screen the messages which originate from the new switch so these signals can be converted to represent the old switch as the source of the signaling. This is done in order to avoid confusion at the destination, but it does not affect the actual selection of the destination. In the prior art system, the destination is not chosen based on the origin of the message. The prior art system uses only trunk identification to choose the destination. This is detected using either the dialed number or the Circuit Identification Code (CIC).
It is also important to note that the prior art system is designed only to convert signaling that has been placed on the signaling link connected to the old switch. This means the STP has already isolated the signaling messages as directed to the old switch. Thus, the system does not see signaling directed to any other switch, and it is not equipped to process signaling that has not been directed to the old switch. As such, an STP incorporating this system would convert the point codes only after the STP has performed routing processing and designated the signaling as being directed to the old switch. Thus, the STP of the prior art system would not apply to a conversion function for incoming signals which had yet to be routed and could still be directed to any switch.
Another prior art system provides a signaling gateway between two signaling systems, for example, a gateway for the signaling systems of Europe and the United States. The signaling gateway converts point codes based on the network identification and the destination point code. The gateway does not convert point codes based on originating information, such as the signaling link or the originating point code. The gateway also converts point codes after the destination point code has been used for message routing. Also, since the gateway must interface signaling of different signaling systems, it necessarily includes more functionality and cost than a point code converter that does not have gateway functionality.
The above-referenced application discloses a signaling processor. The signaling processor receives, processes and transmits signaling. In some instances, the signaling processor will not have a point code to facilitate the routing of signaling messages. In other instances, the signaling processor may receive signaling that was actually transmitted to a switch, but needs to be processed by the signaling processor instead of the switch. The prior art does not address the signaling transfer needs of these signaling processors.
Typically, an STP routes signaling among several switches. Present systems do not provide an efficient and workable STP which can convert signaling in a way that accounts for architectural changes affecting several of the switches. At present, there is a need for an STP that can better facilitate architecture changes in a telecommunications network.